The figure shows the projects_objtab object table with lines connecting the table's attributes projlead_ref and team_ntab to an outlying schematic of the people_objtab object table.
The lines indicate that the attributes of the projects table (projects_objtab) both use REFs to pick out rows in the people object table (people_objtab).
The figure is a graphical representation of the CREATE TYPE projects_objtyp and CREATE TABLE projects_objtab statements that precede the figure in the text.